TabGroup Organizer allows you to save all open tabs as a group and then reopen all with a click. After installation, a new multifolder icon (that gives rise to a context menu when right-clicked) is present on the statusbar in the lower-right corner of the browser window:

Using this Jetpack script, I can finally save tab ensembles and come back to them later -- a real productivity win, for me. Thank you, Davide!

And since the code is open-source, I'm going to reproduce it here (scroll sideways to see the parts that don't wrap):